FIELD OF INVENTION
[0001] Embodiments of the present invention provide a system and method for monitoring the
performance of power filters in power generations systems, and detecting power filter
faults or failures in such systems. In a preferred embodiment, the power generation
systems are high capacity wind turbines.
BACKGROUND
[0002] Power generation systems typically convert one source of power into electrical energy
by turning a rotor of an electrical generator. Power is supplied at a specific voltage
and frequency to an electrical grid, which then transmits the power to the consumer.
In order to ensure that the power is supplied at a constant voltage and frequency,
various control devices/equipment may be used. Ensuring that power is provided at
the desired voltage and frequency may be particularly challenging for wind turbine
generators, which do not turn the rotor of the generator at a constant speed. The
power produced by the turbine must be converted to stable electrical power for transmission.
[0003] For example, one prior art wind turbine generator provides a full power converter
having a generator side active rectifier coupled to a grid side active inverter via
a direct current (DC) link. In this configuration, the active rectifier converts variable
frequency alternating current (AC) signals from the generator into a DC voltage, which
is placed on the DC link. The active inverter converts the DC voltage on the DC link
into fixed frequency AC power for a power grid. Such a configuration requires complicated
and expensive circuitry utilizing active switches (e.g., insulated-gate bipolar transistors
(IGBTs)) for the active rectifier and inverter. These types of active switches typically
have higher power loss during power conversion, and may cause unwanted high frequency
harmonics on the power grid.
[0004] For example, the grid converter may generate switching frequency harmonics at a frequency
of 5 kHz. A grid-side harmonic filter (grid filter) may be used to provide a path
for the switching frequency harmonics and prevent the undesired transmission of the
switching frequency harmonics to the grid utility. The grid filter may be a capacitor
bank that accumulates electrical energy at a variable rate, and discharges the energy
at a controlled rate. The grid filter may be connected to the grid side using, for
example, a fuse.
[0005] One problem associated with currently available wind turbines is that when one or
more of the fuses of the grid filter blow, or some other component of the grid filter
fails, the grid filter cannot function properly. In some of these currently available
systems, when the grid filter fuse blows, there is no feedback signal provided to
the wind turbine control system. As a result, the wind turbine will continue to supply
power to the grid without the grid filter. This in turn may cause other problems,
such as an over-voltage fault alarm or problems connecting to the grid. This problem
may be exacerbated in electrical grids that may suffer from poor overall control.
[0006] One solution to this problem is to provide various electrical components directly
connected to the grid filter to monitor the filter for failures, and report these
failures to an operator via the control system. However, in current systems, it may
be difficult to find components which are easy to install and service, and which meet
various regulatory requirements.
[0007] US patent 4,011,512 discloses a harmonic filter failure detection apparatus for use in single sideband
radio transmitters. The filter is connected to two directional couplers that measure
input and output power from the filter. The two couplers are also connected to a comparator
circuit for detecting power mismatch, and for generating a control signal indicative
of a filter failure.
[0008] It would therefore be an improvement in the art if a system and method could be developed
to overcome one or more of the problems described above.
SUMMARY
[0009] One aspect of the present invention provides a method for determining a fault in
a power filter of a wind turbine generator according to claim 1, a corresponding system
according to claim 8 and a computer readable medium containing a computer program
code according to claim 13. Preferred embodiments are defined in the dependent claims.
The method may include the steps of: calculating a reactive power consumed by the
power filter; and comparing the calculated reactive power to a predefined threshold
reactive power to determine said fault.
[0010] In some embodiments, the calculated reactive power may be based on a measured value
of a converter leg current, and one of a converter leg voltage for each phase wire
of the wind turbine generator. The step of calculating the reactive power consumed
by the power filter may include calculating an average reactive power consumed by
a grid converter leg of the wind turbine generator over a period of time.
[0011] In further embodiments, the step of calculating the average reactive power consumed
by a grid converter leg may further include adjusting the average reactive power consumed
by the grid converter leg by a voltage factor to determine an adjusted average reactive
power consumed by the grid converter leg. The measured values may be obtained substantially
at a transition from a pre-charge state to a run state of the wind turbine generator.
[0012] In alternate embodiments, the step of calculating the reactive power consumed by
the power filter may further include: calculating an adjusted average reactive power
consumed at said pre-charge state by an auxiliary power supply of the wind turbine
generator; calculating an adjusted average reactive power consumed by both the auxiliary
power supply and the power filter in said run state; and calculating the average reactive
power consumed by the grid filter alone based on the values of the average reactive
power consumed by the auxiliary power supply and the average reactive power consumed
by both the auxiliary power supply and the power filter.
[0013] In this embodiment, the step of calculating an adjusted average reactive power consumed
by said auxiliary power supply at said pre-charge state may further include: connecting
a DC link capacitor to a converter leg of said wind turbine generator, pre-charging
said DC link capacitor while said power filter is disconnected; and obtaining said
measured values during said pre-charge state. The step of calculating an adjusted
average reactive power consumed by both the auxiliary power supply and the power filter
in said run state may further include: electrically connecting said power filter;
providing a time delay; calculating said adjusted average reactive power consumed
by both the auxiliary power supply and the power filter over said period of time;
and disconnecting said DC link capacitor.
[0014] In some embodiments, the power filter may be one of a grid-side power filter, a machine
side dv/dt filter, or a stator filter, and said fault may be at least one of a failure
in a fuse, a failure in a capacitor, or a failure in a connection of said power filter.
One fundamental cycle may be .02 seconds and the period of time may be one or more
fundamental cycles.
[0015] An alternate aspect of the present invention provides a system for detecting a fault
in a power filter of a wind turbine generator, the system comprising: a computer processor;
and a plurality of sensors electrically connected to said wind turbine generator and
said computer processor; wherein said computer processor is configured to: calculate
a reactive power consumed by the power filter based on data from said sensors; and
compare the calculated reactive power to a predefined threshold reactive power to
determine said fault.
[0016] In alternate embodiments of the system, the sensors may provide a measured value
of a converter leg current, and one of a converter leg voltage and a stator leg voltage
for each phase wire of the wind turbine generator. The processor may further calculate
an average reactive power consumed by a grid converter leg of the wind turbine generator
over a period of time.
[0017] In other embodiments, the processor may further calculate an average reactive power
consumed by a grid converter leg by adjusting the average reactive power consumed
by the grid converter leg by a voltage factor to determine an adjusted average reactive
power consumed by the grid converter leg. The measured values may be obtained substantially
at a transition from a pre-charge state to a run state of the wind turbine generator.
[0018] In some embodiments, the processor may calculate the reactive power consumed by the
power filter by: calculating an adjusted average reactive power consumed at said pre-charge
state by an auxiliary power supply of the wind turbine generator; calculating an adjusted
average reactive power consumed by both the auxiliary power supply and the power filter
in said run state; and calculating the average reactive power consumed by the grid
filter alone based on the values of the average reactive power consumed by the auxiliary
power supply and the average reactive power consumed by both the auxiliary power supply
and the power filter.
[0019] In further embodiments, the processor may calculate said adjusted average reactive
power consumed by said auxiliary power supply at said pre-charge state by: connecting
a DC link capacitor to a converter leg of said wind turbine generator; pre-charging
said DC link capacitor while said power filter is disconnected; and obtaining said
measured values during said pre-charge state. The processor may calculate said adjusted
average reactive power consumed by both the auxiliary power supply and the power filter
in said run state by: electrically connecting said power filter; providing a time
delay; calculating said adjusted average reactive power consumed by both the auxiliary
power supply and the power filter over said period of time; and disconnecting said
DC link capacitor. One fundamental cycle may be .02 seconds and the period of time
may be one or more fundamental cycles.
[0020] A further aspect of the present invention provides a computer readable medium containing
computer program code for determining a fault in a power filter of a wind turbine
generator, the computer code being configured to: calculate a reactive power consumed
by the power filter; and compare the calculated reactive power to a predefined threshold
reactive power to determine said fault.
[0021] In some embodiments, the calculated reactive power may be based on a measured value
of a converter leg current and a converter leg voltage/ a stator leg voltage for each
phase wire of the wind turbine generator. The step of calculating the reactive power
consumed by the power filter may further include calculating an average reactive power
consumed by a grid converter leg of the wind turbine generator over a period of time.
[0022] In alternate embodiments, the step of calculating the average reactive power consumed
by a grid converter leg may further include adjusting the average reactive power consumed
by the grid converter leg by a voltage factor to determine an adjusted average reactive
power consumed by the grid converter leg. The measured values may be obtained substantially
at a transition from a pre-charge state to a run state of the wind turbine generator.
[0023] In further embodiments, the step of calculating the reactive power consumed by the
power filter may further include: calculating an adjusted average reactive power consumed
at said pre-charge state by an auxiliary power supply of the wind turbine generator;
calculating an adjusted average reactive power consumed by both the auxiliary power
supply and the power filter in said run state; and calculating the average reactive
power consumed by the grid filter alone based on the values of the average reactive
power consumed by the auxiliary power supply and the average reactive power consumed
by both the auxiliary power supply and the power filter.
[0024] In other embodiments, the step of calculating an adjusted average reactive power
consumed by said auxiliary power supply at said pre-charge state may further include:
connecting a DC link capacitor to a converter leg of said wind turbine generator;
pre-charging said DC link capacitor while said power filter is disconnected; and obtaining
said measured values during said pre-charge state. The step of calculating an adjusted
average reactive power consumed by both the auxiliary power supply and the power filter
in said run state may further include: electrically connecting said power filter;
providing a time delay; calculating said adjusted average reactive power consumed
by both the auxiliary power supply and the power filter over said period of time;
and disconnecting said DC link capacitor.
[0025] The power filter may be one of a grid-side power filter, a machine side dv/dt filter,
or a stator filter. The fault may be at least one of a failure in a fuse, a failure
in a capacitor, or a failure in a connection of said power filter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Embodiments of the invention will be better understood and readily apparent to one
of ordinary skill in the art from the following written description, by way of example
only, and in conjunction with the drawings, in which:
Figure 1 illustrates a simplified schematic diagram of a wind turbine generator in
which embodiments of the present invention may be used to determine a power filter
failure;
Figure 2 illustrates a circuit diagram of a wind turbine generator in which embodiments
of the present invention may be used to determine a power filter failure;
Figure 3 illustrates a close-up view of a portion of the circuit diagram of Figure
2 showing the grid inverter and power filter;
Figure 4A illustrates a schematic diagram of one embodiment of a grid filter shown
in Figures 2 and 3;
Figure 4B illustrates a schematic diagram showing a normal operating mode for the
grid filter of Figure 4A;
Figure 4C illustrates a schematic diagram showing one possible failure mode for the
grid filter of Figure 4A;
Figure 4D illustrates a schematic diagram showing an alternate possible failure mode
for the grid filter of Figure 4A;
Figure 4E illustrates a schematic diagram showing another alternate possible failure
mode for the grid filter of Figure 4A;
Figure 5 is a graph illustrating one possible implementation of a detection process
that may be used with the system and method of the present invention;
Figure 6 illustrates a flow chart showing one possible implementation of the method
of the present invention; and
Figure 7 illustrates a schematic diagram of one possible computer system that may
be used to implement the system and method of the present invention.
DETAILED DESCRIPTION
[0027] Embodiments of the present invention provide a system and method to alert an operator
of an electrical generation system of a failure in a power filter without requiring
the installation of additional hardware components. For the purposes of illustration,
one embodiment of the present system and method will be described below with respect
to a wind turbine generator producing three-phase power. However, it is understood
that other types and sizes of generators, both single phase and multiple phase, may
also be used, without departing from the scope of the present embodiments, as defined
by the appended claims. By way of example, embodiments of the present invention may
be used with doubly/singly fed induction generators, synchronous generators including
permanent magnet (PM), interior permanent magnet (IPM), and surface mounted permanent
magnet (SMPM) generators, asynchronous generators including induction generators (IG),
squirrel cage generators, and other types of generators known to those of skill in
the art. Full-scale electrical systems may also be considered.
[0028] Similarly, while the discussion below focuses on an example embodiment in which the
power filter is a grid-side filter, it is understood that other types and locations
of power filters may also be used with embodiments of the present invention. The method
of determining a failure in a power filter may be applied to any filter in an electrical
power generator, and more particularly a wind turbine generator. By way of example
and not limitation, such filters may include machine side dv/dt filters, stator filters,
or any other type of power filter that is capable of filtering out the switching frequency
harmonics. For the purpose of discussion, the term "grid filter" used below applies
to all such power filters.
[0029] Figure 1 illustrates a simplified schematic diagram of a wind turbine generator (WTG)
system 10 in which embodiments of the present invention may be used to determine a
power filter failure. The WTG system 10 may be a PM, IPM, SMPM or IM system as described
above. The WTG system 10 includes a rotor blade 20 connected by an input shaft 22
to an optional gearbox 24. The gearbox 24 is connected via an output shaft 26 to a
WTG 30, which converts the rotary motion of the rotor blade 20 into electric power.
The optional gearbox 24 may be used to increase the rotational speed of the output
shaft 26.
[0030] In this embodiment, the WTG 30 is configured to supply power to a fixed-frequency
(typically 50 or 60 Hz) power grid 130. One way for the WTG 30 to provide synchronized
power to the grid 130 would be to ensure that the rotor blade 20 turns at a constant
speed. However, in order to provide higher efficiency in the production of electricity,
the speed of the rotor blade 20 may be allowed to vary within a certain range. This
allows the rotor blade 20 to rotate at an optimum speed for any given wind speed.
The WTG 30 may thus produce AC power that is not synchronised with the power grid
130.
[0031] To alleviate this problem, an AC/DC converter 35 may be connected to the stator windings
of the WTG 30 via power lines 31 a, 31b, and 31c. The AC/DC converter 35 converts
the AC power output from the WTG 30 to DC power. The AC/DC converter 35 is connected
via a filter capacitor 36 to a DC/AC converter 40, which converts the DC power to
AC power that is synchronised with the power grid 130. In some configurations, a transformer
(not shown) may be placed between the DC/AC converter 40 and the grid 130. One or
more power filters 42 and/or grid filters 44 may be electrically connected to the
output power lines 45a, 45b, and 45c, which connect to the transformer and the grid
130.
[0032] Figure 2 illustrates a circuit diagram 100 of a wind turbine generator 150 in which
embodiments of the present invention may be used to determine the status of a grid
filter 102 and to report any failure in the grid filter 102 to an operator of the
system. In this embodiment, the WTG 150 is a doubly fed induction generator (DFIG).
However, as outlined above, it is understood that embodiments of the present invention
may be used with any type of WTG. The DFIG WTG 150 includes a stator (not shown) having
a three phase winding which is connected through a circuit breaker 152 via power lines
154a, 154b and 154c directly to the transmission grid 130 through a step up voltage
transformer 156. The current on the power lines 154a, 154b, 154c flowing into the
main electrical grid 130 may be measured using pre-existing transducers 155a, 155b
and 155c. In the discussion which follows, power lines 154a, 154b and 154c form the
"stator leg", and the current measured using transducers 155a, 155b, and 155c will
be known as the stator leg current. It is understood that other types and locations
of measurement devices that function to measure the stator leg current and/or the
stator leg voltage may also be used. The three phase rotor winding (not shown) is
connected via a slip ring and brush assembly (not shown) to the rotor side of a power
converter 120 via power lines 158a, 158b and 158c.
[0033] The power converter 120 includes an AC/DC machine-side rectifier 122, a DC-link 124,
and a DC/AC grid inverter 126. The grid filter 102 is connected to the output of the
grid inverter 126 via power lines 128a, 128b, and 128c. The three phase filtered power
is then provided through a first circuit breaker/switch 131 and a second circuit breaker/switch
133 to the transformer 156 and the main electrical grid 130 via power lines 140a,
140b and 140c. A wind turbine auxiliary power supply 142 may be provided to power
certain components in the wind turbine under some circumstances. The auxiliary power
supply 142 may consume power from the main grid 130, or from the grid inverter 126.
The current on the power lines 140a, 140b, 140c flowing into the main electrical grid
130 may be measured using pre-existing transducers 160a, 160b and 160c. In the discussion
which follows, power lines 140a, 140b and 140c form the "grid converter leg", and
the current measured using transducers 160a, 160b, and 160c will be known as the converter
leg current. This will be discussed in more detail below. It is understood that other
types and locations of measurement devices that function to measure the converter
leg current and/or the converter leg voltage may also be used.
[0034] In this embodiment, the circuit breaker/switch 131 may be used to disconnect the
power output from the power converter 120 during a fault or other condition. Similarly,
the circuit breaker/switch 133 may be used to disconnect the power output from the
power converter 120 and auxiliary power supply 142 from the main grid 130 during a
fault or other condition.
[0035] Figure 3 illustrates a close-up view of the grid inverter 126 and grid filter 102
shown in Figure 2. In this embodiment, the grid filter 102 is installed between the
grid chokes/connector switches 104, 106 and the circuit breaker 133. The grid filter
102 is connected to point 132c, 132b, and 132a on power lines 140c, 140b, and 140a
through grid fuse 134c, 134b, and 134a, respectively. A pre-charge circuit, illustrated
as switch 108 and pre-charge resistors 109 may be used to power up a DC link capacitor
125 within the DC link 124 prior to generator startup or connection of the machine-side
converter. During pre-charge, the switches 104, 106 are disconnected. During normal
operation, once the voltage measured across the DC Link capacitor 125 reaches a target
value, switches 104 and 106 are switched on, and switch 108 is switched off. However,
the method of the present invention allows switch 108 to remain on for a period of
time. This will be discussed in much greater detail below.
[0036] One example of a schematic diagram for the grid filter 102 is shown in Figure 4A.
In this embodiment, the grid filter 102 includes a first capacitor bank 102a, a second
capacitor bank 102b, and a discharge coil 102c. Each capacitor bank 102a, 102b is
electrically connected to the power lines 128a, 128b, and 128c via output lines 136a,
136b, and 136c respectively. Similarly, the discharge coil 102c is electrically connected
to the power lines 128a, 128b, and 128c. When the grid filter 102 is switched off
for any reason, any residual DC voltage remaining in the capacitors 102a, 102b may
be discharged very quickly through the discharge coil 102c. This helps to ensure a
short reconnect time when the grid filter 102 is switched back on.
[0037] It is understood that other configurations of the grid filter 102 may also be used.
For example, the grid filter 102 may include one or more capacitor banks, which may
be connected in different configurations. The capacitors used in the capacitor banks
may be self healing. All such configurations for the grid filter 102 are deemed to
fall within the scope of the appended claims, provided that these configurations function
to filter the supplied power including, but not limited to, the switching frequency
harmonics.
[0038] Figure 4B illustrates the normal operating mode for the grid filter 102 shown in
Figure 4A. In the normal operating mode, all three-phase grid filters 102a, 102b have
been connected, and none of grid filter fuses are blown.
[0039] Figures 4C-4E illustrate grid filter 102 failure modes. The failure mode for the
self healing type capacitors 102a, 102b used in the grid filter 102, is normally a
slow degrading of the capacitance, i.e. the capacitance will decrease over time. Common
failure modes for the grid filter 102 may include a failure of one or more of the
fuses 134a, 134b, 134c, or the contactors. Figure 4C illustrates the case in which
one of the grid filter fuses/contactors (134c) fails resulting in the disconnection
of one of the capacitors 103a. Figure 4D illustrates the case in which two of the
grid filter fuses/contactors fail (134b, 134c) resulting in the disconnection of two
of the capacitors 103a, 103b. Figure 4E illustrates the case in which all of the grid
filter fuses/contactors fail resulting in the disconnection of all of the capacitors
103a, 103b, 103c. For the purposes of the discussion which follows, when the grid
filter 102 works properly, all three-phase grid filter branches are working and none
of the grid filter fuses/contactors/capacitors are blown. Grid filter failure may
include any fuse failure, any grid filter contactors failure, any capacitors failure,
or any other failure of a component in the grid filter 102.
[0040] In an alternating current electrical system, the term "reactive power" is used to
represent the energy alternately stored and released by inductors and/or capacitors.
In the present embodiments, an instantaneous reactive power concept may be used. The
instantaneous reactive power consumed by the grid filter 102 shown in Figures 4A-4E
is discussed below with reference to Equations 1-4.
[0041] For the purpose of discussion, it is assumed that the grid voltage varies within
a range of 0.8 power units (p.u.) and 1.2 p.u. Therefore, given that the reactive
power is calculated as the square of the voltage units, the reactive power under normal
mode is within a range of 0.64Q
nom - -1.44Q
nom.
[0042] For the failure mode illustrated in Figure 4C, the reactive power consumed by the
grid filter 102 is approximately half of the reactive power consumed under the normal
mode. Therefore, the range of reactive power in this case is 0.32* Q
nom - 0.72* Q
nom For the failure modes illustrated in Figures 4D and 4E, the reactive power consumed
by the grid filter 102 is zero.
[0043] For purposes of illustration, it is assumed that the capacitors 103a-103c are rated
at 56 KVar at a voltage of 440V, and the nominal voltage of the grid tapping is 400V
(Line-Line), with a nominal frequency of either 50Hz or 60Hz, depending on the location
of the grid. The value of the nominal reactive power Q
nom may then be computed using the following formula:
where Cap is the capacitor rating, V
cap is the voltage rating of the capacitor, and V
grid is the nominal voltage rating of the grid.
[0044] The value of Q
nom for the capacitor 102 would thus be 46.44kVar at nominal voltage for the generator
discussed herein. However, it is understood that the value of Q
nom may change depending on the type of capacitors used, the capacity of the wind turbine
generator, the line-line voltage, etc.
[0045] Embodiments of the system and method of the present invention provide a means to
measure the reactive power consumed by the grid filter 102 during each of the modes
discussed above, using only existing inputs. The measurements may then be used to
determine a failure mode of the grid filter 102, which is then reported to a supervision
system that generates an alarm if the grid filter 102 fails. The measurements are
accomplished by comparing the mean values of the reactive power before and after switches
104 and 106 are closed. One assumption being made here is that the auxiliary power
supply 142 is not cycled on and off during the failure detecting process.
[0046] Figure 5 is a graph illustrating one possible implementation of a detection process,
designated generally as reference numeral 300, which may be used with the system and
method of the present invention. Figure 6 illustrates a flow chart, designated generally
as reference numeral 400, showing one possible implementation of the method of the
present invention.
[0047] In this embodiment, the various signals available to monitor and detect grid filter
102 failures are summarised in Table 1 below:
where MGC_ILx represents the current sent to the grid 130 on the grid converter leg,
measured, for example, using transducers 160a, 160b and 160c, and including the current
from the grid converter 126 and the current from the auxiliary power supply 142; and
MGS_ULx are the voltages of the stator leg measured at a point between the switch
152 and the high voltage transformer 156. MGC_ULx represents the voltages of the each
phase wire of the gird converter leg, and may be measured with voltage sensors located
near transducers 160. It is understood that other measurement points may also be used.
[0048] The reactive power q consumed on the grid converter leg may then be calculated using
Formula 1 as follows:
where, MGC_ILx and MGC_ULx are defined above for the grid converter leg in the a-b-c
original frame, MGC_v
α and MGC_v
β denote the main grid converter leg voltages in α-β frame, and MGC_i
α and MGC_i
β denote the main grid converter leg currents in α-β frame wherein:
[0049] Formula 4 may be required in cases in which the voltage sensors for directly measuring
the value of MGC_ULx are not available. The value of MGS_ULx represents the stator
leg voltages as measured, and are multiplied by the turn ratio of the transformer
156 to determine MGC_ULx. In some embodiments, the definition of q in the a-b-c frame
may be used. Alternately, the transformation to the α-β frame may be used.
[0050] In an embodiment, the WTG system is a full scale electrical system and the generator
electrical output is provided into a back-to-back power converter which is thereafter
coupled to a grid filter. Direct measurements of a current and a voltage of a grid
converter leg are measured to determine the reactive power consumption of the grid
filter.
[0051] With continuing reference to Figure 6, the method 400 begins with a first step of
enabling the power filter check and setting all of the variables to zero, as shown
with reference numeral 402. This enabling step may be accomplished, for example, when
an operator of the system initiates a software program on one or more control microprocessors
that receive data from, and provide various control functions to, the system.
[0052] As discussed above, the method 400 uses the average values of the reactive power.
In order to determine the average values for the reactive power, a sampling period
should be determined. For purposes of illustration, we will use 100 microseconds (µs)
as the sampling period. It is understood that other sampling periods may also be used.
Using a sampling period of 100 µs, the average reactive power of the grid converter
leg in a fundamental cycle (0.02 seconds) may be computed as:
[0053] In this embodiment, the reactive power calculated in Equations (1) and (5) includes
both the reactive power consumed by the wind turbine auxiliary power supply 142 and
by the grid filters 102 (see Fig. 1). In order to determine the reactive power consumed
by the grid filter 102 alone, there are a number of factors to consider.
[0054] First, it may be noted that there is an overlap area between the normal case (Figure
4B) and the first failure case (Figure 4C). As previously discussed, the reactive
power consumed by the grid filter in the normal mode is between 0.64Q
nom - 1.44Q
nom. The reactive power consumed by the grid filter in the first failure case is half
of the reactive power consumed in the normal mode, i.e. between 0.32Q
nom - 0.72Q
nom. To compensate for the overlap in these ranges, a voltage factor may be introduced
in the average reactive power computation (Equation 5) to eliminate the effect of
grid voltage variations. This may be shown as:
where
Q is the adjusted average reactive power of the grid converter leg, and the voltage
factor
Ufactor is defined as:
and
Unom is the nominal grid voltage.
[0055] The second factor to consider is the fact that the values of
q and
Q calculated above are dependent on the specific electrical circuit configuration shown
in Figures 1 and 2. The reactive power
q and
Q could contain reactive power consumed by both the auxiliary power supply 142 and
the grid filter 102. To obtain the reactive power consumed by the grid filter 102
alone, the reactive power before and after switches 104 and 106 are closed may be
calculated and compared. Two different stages, Stage a and Stage b, which provide
a transition between a "pre-charge" state and a "run" state for the wind turbine generator,
are considered below.
[0056] In Stage a, the switch 108 is set to ON, and switches 104 and 106 are OFF, as shown
with reference numeral 404 in Figure 6. The DC-link capacitor 125 (Figure 3) is then
charged through one or more pre-charge resistors 109. During this stage, the values
of the reactive power
q and
Q include only the reactive power consumed by the wind turbine auxiliary power supply
142.
[0057] In Stage b, when the DC-link voltage reaches a certain voltage, for example 500V,
switches 104 and 106 are turned on and the grid filter 102 is connected. During this
"run" stage, the values of the reactive power and
Q include both the reactive power consumed by the wind turbine auxiliary power supply
142 and by the grid filter 102.
[0058] In this embodiment, if the auxiliary power supply 142 consumes the same amount of
reactive power during Stage a and Stage b, the reactive power difference between Stage
a and Stage b is the reactive power consumed by the grid filter 102. However, the
auxiliary power supply 142 may not always consume the same amount of reactive power
in both stages. For example, during normal operation, the wind turbine generator may
yaw automatically to keep the nacelle directly upwind. A cooling system (not shown)
may be automatically engaged to cool the power generator 120. Therefore, there is
a possibility that some auxiliary power from the auxiliary power supply 142 will be
required during Stage b. Thus, the reactive power difference between Stage a and Stage
b may not represent the reactive power consumed by the grid filter 102.
[0059] To reduce the possibility that the auxiliary power supply 142 is cycled on and off
during the grid filter failure detection process, and obtain the grid filter reactive
power, the detecting process may be made both continuous and short, and the consistency
of the data may be checked. With reference to Figure 5 the graph 300 shows the on-off
states of switches 104, 106 and 108 on the left axis 301 plotted against time in seconds
on the lower axis 303. Note that switches 104 and 106 are engaged simultaneously to
connect the grid filter 102. However, it is understood that various electrical configurations
including a greater or lesser number of switches may also be used.
[0060] As illustrated in the graph 300, right before switches 104 and 106 are turned on,
and while switch 108 is turned on, 10 fundamental-cycle reactive power data may be
processed to obtain an average value of the reactive power during Stage a (
Q _
a), as shown with reference numeral 302 in Figure 5, and reference numeral 406 in Figure
6. It is understood that a greater or lesser number of fundamental cycles may also
be used as a desired time period. The calculation of the value of
ΔQ shown in step 406 is discussed in more detail below.
[0061] Following that, a 0.1 second time delay may be inserted to avoid the transient period
associated with the closing of switches 104 and 106, as shown with reference numeral
304 in Figure 5, and reference numeral 408 in Figure 6. It is understood that other
values for the desired time delay, both longer and shorter than 0.1 second, may also
be used. Next, switches 104 and 106 are turned on, as shown with reference numeral
410.
[0062] Thereafter, another 10 fundamental-cycle of reactive power data may be processed
to obtain an average value of the reactive power during stage b (
Q_
b), as shown with reference numeral 306 in Figure 5, and reference numeral 412 in Figure
6. The calculation of the value of
ΔQ shown in step 412 is discussed in more detail below. For this example, only 0.5 seconds
are thus required for the entire detecting process. It is understood, as discussed
above, that other time periods, time delays and numbers of cycles, both shorter and
longer, may also be used.
[0063] In order to determine that the auxiliary power supply 142 has not cycled on and off
during the monitoring process, as shown with reference numeral 414, the consistency
of the two sets of 10-fundamental-cycle data may be checked. The procedure to check
the data is discussed below.
[0064] The average value of one-fundamental-cycle data may be defined as
where,
Q_a1 ∼ Q_
a10 and
Q_ b1 ∼
Q_
b10 are calculated based on Equation 6 defined above.
[0065] To determine that the auxiliary power supply 142 has not cycled on and off during
the detecting process, the following equations should be satisfied:
where the average reactive power for stage a and stage b are
And Δ
Q and [
Q_Min Q_Max] are values selected by the operator of the wind turbine generator. By way of example
and not limitation, Δ
Q could be selected as 0.05
Qnom and [
Q_
Min Q_Max] could be selected as [-0.2Q
nom 1.2
Qnom]. Note that the values for Δ
Q are calculated during steps 406 and 412 as discussed above.
[0066] If Equations 13-15 are not satisfied, then the auxiliary power supply 142 has cycled
on and off during the detecting process. In this case, the power filter check may
be terminated, as shown with reference numerals 416 and 417.
[0067] If Equations 13-15 are satisfied, the auxiliary power supply 142 has not cycled on
and off during the detecting process, as shown with reference numeral 418. The average
reactive power consumed by the grid filter is then obtained as
as shown with reference numeral 420.
[0068] The value for the reactive power
Q calculated above may then be compared to a desired value, i.e. a threshold reactive
power, to determine if a power filter fault has been detected, as shown with reference
numeral 422. By way of example and not limitation, a fault condition may be generated
if:
where
Qnom denotes the reactive power consumed under the normal operating mode with nominal
grid voltage, as previously defined. It is understood that the specific percentage
of
Qnom that is to be used may be defined by the system administrator of the wind turbine
generator, so that it can be easily adjusted during testing and operation. Similarly,
a value of "
Q/
Qnom" may be defined by the system administrator as well. Therefore, Equation 19 can be
written as Equation 20 below:
[0069] If Equation 20 is not satisfied, the value of Q is within acceptable limits, as shown
with reference numeral 426. Normal operation of the WTG may then begin, as shown with
reference numeral 428.
[0070] However, if Equation 20 is satisfied, a fault condition has been determined, as shown
with reference numeral 430. An error message may then be sent to the operator such
as "Filter capacitor value too low calculated to: xxxx p.u., has to be above xxxx
p.u.", as shown with reference numeral 432.
[0071] In an embodiment, a diagnostic system is provided for the wind turbine system 10.
The diagnostic system may comprise capabilities to test and diagnose the electrical
system as well as individual components such as generators, transformers, contactors,
filters, semiconductor switching devices and so on. Method 400, as described above,
is used to monitor the grid filter 102 is implemented as part of the diagnostic system.
A filter temperature monitoring scheme may also be implemented to complement method
400.
[0072] Other testing methods may also be used in such an electrical system diagnostic system,
either for the grid filter 102, any other individual component, or for a collection
of components. For example, enclosure temperature testing, electrical parameter monitoring,
frequency response analysis, partial discharge detection, or any other testing scheme
may be used as part of the diagnostic system. Such a diagnostic system may also comprise
functionality such as control of certain individual components, or a collection of
components in the system. The diagnostic system could also modify the power production
of the wind turbine generator in response to certain faults detected, or to shut down
the turbine pre-emptively. It may also have an input into the maintenance schedule
of the wind turbine, bringing forward a maintenance call, in response to a determination
that a component is close to failure.
[0073] Some portions of the description above are explicitly or implicitly presented in
terms of algorithms and functional or symbolic representations of operations on data
within a computer memory. These algorithmic descriptions and functional or symbolic
representations are the means used by those skilled in the data processing arts to
convey most effectively the substance of their work to others skilled in the art.
An algorithm is here, and generally, conceived to be a self-consistent sequence of
steps leading to a desired result. The steps are those requiring physical manipulations
of physical quantities, such as electrical, magnetic or optical signals capable of
being stored, transferred, combined, compared, and otherwise manipulated.
[0074] Unless specifically stated otherwise, and as apparent from the following, it will
be appreciated that throughout the present specification, discussions utilizing terms
such as "scanning", "calculating", "determining", "replacing", "generating", "initializing",
"outputting", or the like, refer to the action and processes of a computer system,
or similar electronic device, that manipulates and transforms data represented as
physical quantities within the computer system into other data similarly represented
as physical quantities within the computer system or other information storage, transmission
or display devices.
[0075] The present specification also discloses apparatus, such as the processor 110, for
performing the operations of the methods. Such apparatus may be specially constructed
for the required purposes, or may comprise a general purpose computer or other device
selectively activated or reconfigured by a computer program stored in the computer.
The algorithms and displays presented herein are not inherently related to any particular
computer or other apparatus. Various general purpose machines may be used with programs
in accordance with the teachings herein. Alternatively, the construction of more specialized
apparatus to perform the required method steps may be appropriate. The structure of
a conventional general purpose computer will appear from the description below.
[0076] In addition, the present specification also implicitly discloses a computer program,
in that it would be apparent to the person skilled in the art that the individual
steps of the method described herein may be put into effect by computer code. The
computer program is not intended to be limited to any particular programming language
and implementation thereof. It will be appreciated that a variety of programming languages
and coding thereof may be used to implement the teachings of the disclosure contained
herein. Moreover, the computer program is not intended to be limited to any particular
control flow.
[0077] Furthermore, one or more of the steps of the computer program may be performed in
parallel rather than sequentially. Such a computer program may be stored on any computer
readable medium. The computer readable medium may include storage devices such as
magnetic or optical disks, memory chips, or other storage devices suitable for interfacing
with a general purpose computer. The computer readable medium may also include a hard-wired
medium such as exemplified in the Internet system, or wireless medium such as exemplified
in the GSM mobile telephone system. The computer program when loaded and executed
on such a general-purpose computer effectively results in an apparatus that implements
the steps of the preferred method.
[0078] The invention may also be implemented as hardware modules. More particularly, in
the hardware sense, a module is a functional hardware unit designed for use with other
components or modules. For example, a module may be implemented using discrete electronic
components, or it can form a portion of an entire electronic circuit such as an Application
Specific Integrated Circuit (ASIC). Numerous other possibilities exist. Those skilled
in the art will appreciate that the system can also be implemented as a combination
of hardware and software modules.
[0079] The method and system of the example embodiment can be implemented on a computer
system 500, schematically shown in Figure 7. It may be implemented as software, such
as a computer program being executed within the computer system 500, and instructing
the computer system 500 to conduct the method of the example embodiment.
[0080] The computer system 500 can include a computer module 502, input modules such as
a keyboard 504 and mouse 506 and a plurality of output devices such as a display 508,
and printer 510. It is understood that both the computer system 500 and the various
input and output devices may be located remotely from the Wind turbine generator 100.
Alternately, portions of the computer system 500 may be located with the Wind turbine
generator 100, while other portions are located remotely. It is also understood that
multiple computer systems may be used to implement various parts of the method 400
as described above.
[0081] The computer module 502 can be connected to a computer network 512 via a suitable
transceiver device 514, to enable access to e.g. the Internet or other network systems
such as Local Area Network (LAN) or Wide Area Network (WAN).
[0082] The computer module 502 in the example includes a processor 518, a Random Access
Memory (RAM) 520 and a Read Only Memory (ROM) 522. The computer module 502 also includes
a number of Input/Output (I/O) interfaces, for example I/O interface 524 to the display
508, and I/O interface 526 to the keyboard 504. The components of the computer module
502 typically communicate via an interconnected bus 528 and in a manner known to the
person skilled in the relevant art.
[0083] The application program can be supplied to the user of the computer system 500 encoded
on a data storage medium such as a CD-ROM or flash memory carrier and read utilizing
a corresponding data storage medium drive of a data storage device 530. The application
program is read and controlled in its execution by the processor 518. Intermediate
storage of program data maybe accomplished using RAM 720.
[0084] Embodiments of the present invention provide several advantages. Since the system
and method may be implemented using currently available voltage and current measurements,
no additional hardware need be installed on the WTG. The system and method provide
a low cost option for determining a fault condition in one or more power filters connected
to the WTG. The current system and method may thus be used to alert an operator of
a power filter failure before any damage may occur to the components of the WTG.
[0085] Embodiments of the present invention provide a system and method to accurately detect
all power filter failures. The method provides checks to indicate if the detecting
result is not accurate. The method can detect power filter failures not only under
nominal voltage but also under allowed operating grid voltages.
1. A method for determining a fault in a power filter (102) of a wind turbine generator
(30, 150), the method comprising the steps of:
calculating a reactive power consumed by the power filter; and
comparing the calculated reactive power to a predefined threshold reactive power to
determine said fault,
wherein said calculated reactive power is based on a measured value of a converter
leg current and one of a converter leg voltage for each phase wire of the wind turbine
generator,
characterized in that
said measured values are obtained at a transition from a pre-charge state to a run
state of the wind turbine generator, wherein the pre-charge state consists in pre-charging
of a DC link capacitor connected to one of a converter leg of the wind turbine generator,
while the power filter is disconnected.
2. The method of claim 1, wherein the step of calculating the reactive power consumed
by the power filter comprises calculating an average reactive power consumed by a
grid converter leg of the wind turbine generator over a period of time.
3. The method of claim 2, wherein the step of calculating the average reactive power
consumed by a grid converter leg further comprises adjusting the average reactive
power consumed by the grid converter leg by a voltage factor to determine an adjusted
average reactive power consumed by the grid converter leg.
4. The method of claim 1, wherein the step of calculating the reactive power consumed
by the power filter further comprises:
calculating an adjusted average reactive power consumed at said pre-charge state by
an auxiliary power supply (142) of the wind turbine generator;
calculating an adjusted average reactive power consumed by both the auxiliary power
supply and the power filter in said run state; and
calculating the average reactive power consumed by the power filter alone based on
the values of the average reactive power consumed by the auxiliary power supply and
the average reactive power consumed by both the auxiliary power supply and the power
filter.
5. The method of claim 4, wherein:
the step of calculating an adjusted average reactive power consumed by said auxiliary
power supply at said pre-charge state further comprises:
connecting the DC link capacitor (125) to a converter leg of said wind turbine generator;
pre-charging said DC link capacitor while said power filter is disconnected; and
obtaining said measured values during said pre-charge state;
the step of calculating an adjusted average reactive power consumed by both the auxiliary
power supply and the power filter in said run state further comprises:
electrically connecting said power filter;
providing a time delay;
calculating said adjusted average reactive power consumed by both the auxiliary power
supply and the power filter over said period of time; and
disconnecting said DC link capacitor.
6. The method of any one of claims 2-4, wherein one fundamental cycle is .02 seconds
and the period of time is one or more fundamental cycles.
7. The method of any one of the previous claims, wherein said power filter is one of
a grid-side power filter, a machine side dv/dt filter, or a stator filter, and said
fault is at least one of a failure in a fuse, a failure in a capacitor, or a failure
in a connection of said power filter.
8. A system for detecting a fault in a power filter (102) of a wind turbine generator
(30, 150), the system comprising:
a computer processor (518); and
a plurality of sensors (155, 160) electrically connected to said wind turbine generator
and said computer processor; wherein
said computer processor is configured to:
calculate a reactive power consumed by the power filter based on data from said sensors;
and
compare the calculated reactive power to a predefined threshold reactive power to
determine said fault,
wherein said sensors provide a measured value of a converter leg current and one of
a converter leg voltage for each phase wire of the wind turbine generator,
characterized in that
said measured values are obtained at a transition from a pre-charge state to a run
state of the wind turbine generator, wherein the pre-charge state consists in pre-charging
of a DC link capacitor connected to one of a converter leg of the wind turbine generator,
while the power filter is disconnected.
9. The system of claims 8, wherein said processor calculates an average reactive power
consumed by a grid converter leg of the wind turbine generator over a period of time.
10. The system of claim 9, wherein said processor further calculates an average reactive
power consumed by a grid converter leg by adjusting the average reactive power consumed
by the grid converter leg by a voltage factor to determine an adjusted average reactive
power consumed by the grid converter leg.
11. The system of any of claims 8-10, wherein the processor calculates the reactive power
consumed by the power filter by:
calculating an adjusted average reactive power consumed at a pre-charge state by an
auxiliary power supply of the wind turbine generator;
calculating an adjusted average reactive power consumed by both the auxiliary power
supply and the power filter in a run state; and
calculating the average reactive power consumed by the grid filter alone based on
the values of the average reactive power consumed by the auxiliary power supply and
the average reactive power consumed by both the auxiliary power supply and the power
filter.
12. The system of claim 11, wherein:
said processor calculates said adjusted average reactive power consumed by said auxiliary
power supply at said pre-charge state by:
connecting the DC link capacitor to a converter leg of said wind turbine generator;
pre-charging said DC link capacitor while said power filter is disconnected; and
obtaining said measured values during said pre-charge state; and
said processor calculates said adjusted average reactive power consumed by both the
auxiliary power supply and the power filter in said run state by:
electrically connecting said power filter;
providing a time delay;
calculating said adjusted average reactive power consumed by both the auxiliary power
supply and the power filter over said period of time; and
disconnecting said DC link capacitor.
13. A computer readable medium containing computer program code for determining a fault
in a power filter of a wind turbine generator, the computer code being configured
to operate the method as claimed in any of claims 1 to 7.
1. Verfahren zum Bestimmen eines Defektes in einem Stromfilter (102) eines Windturbinengenerators
(30, 150), das Verfahren umfassend die Schritte:
Berechnen einer Blindleistung, die von dem Stromfilter verbraucht wird; und
Vergleichen der berechneten Blindleistung mit einem vorgegebenen Schwellenwert der
Blindleistung, um den Defekt festzustellen,
wobei die berechnete Blindleistung auf einem gemessenen Wert eines Wandlerschenkelstromes
und einer Wandlerschenkelspannung für jeden Phasendraht des Windturbinengenerators
basiert,
dadurch gekennzeichnet, dass
die gemessenen Werte bei einem Übergang von einem Vorladezustand zu einem Laufzustand
des Windturbinengenerators erhalten werden,
wobei der Vorladezustand im Vorladen eines Gleichstrom-Zwischenkreiskondensators,
der mit einem der Wandlerschenkel des Windturbinengenerators verbunden ist, besteht,
während der Stromfilter abgetrennt ist.
2. Verfahren nach Anspruch 1, wobei der Schritt Berechnen der Blindleistung, die von
dem Stromfilter verbraucht wird, umfasst Berechnen einer durchschnittlichen Blindleistung,
die von einem Netzwandlerschenkel eines Windturbinengenerators über einen Zeitraum
verbraucht wird.
3. Verfahren nach Anspruch 2, wobei der Schritt Berechnen der durchschnittlichen Blindleistung,
die von einem Netzwandlerschenkel verbraucht wird, weiterhin umfasst Anpassen der
durchschnittlichen Blindleistung, die von dem Netzwandlerschenkel verbraucht wird,
mit einem Spannungsfaktor, um eine angepasste durchschnittliche Blindleistung, die
von dem Netzwandlerschenkel verbraucht wird, zu bestimmen.
4. Verfahren nach Anspruch 1, wobei der Schritt Berechnen der Blindleistung, die von
dem Stromfilter verbraucht wird, weiterhin umfasst:
Berechnen einer angepassten durchschnittlichen Blindleistung, die in dem Vorladezustand
von einer Hilfsstromversorgung (142) des Windturbinengenerators verbraucht wird;
Berechnen einer angepassten durchschnittlichen Blindleistung, die im Laufzustand sowohl
von der Hilfsstromversorgung wie auch von dem Stromfilter verbraucht wird; und
Berechnen der durchschnittlichen Blindleistung, die alleine von dem Stromfilter verbraucht
wird, basierend auf den Werten der durchschnittlichen Blindleistung, die von der Hilfsstromversorgung
verbraucht wird, und der durchschnittlichen Blindleistung, die sowohl von der Hilfsstromversorgung
wie auch von dem Stromfilter verbraucht wird.
5. Verfahren nach Anspruch 4, wobei:
der Schritt Berechnen einer angepassten durchschnittlichen Blindleistung, die in dem
Vorladezustand von einer Hilfsstromversorgung verbraucht wird, weiterhin umfasst:
Verbinden des Gleichstrom-Zwischenkreiskondensators (125) mit einem Wandlerschenkel
des Windturbinengenerators;
Vorladen des Gleichstrom-Zwischenkreiskondensators während der Stromfilter abgetrennt
ist; und
Erlangen der gemessenen Werte während des Vorladezustandes;
der Schritt Berechnen einer angepassten durchschnittlichen Blindleistung, die im Laufzustand
sowohl von der Hilfsstromversorgung wie auch von dem Stromfilter verbraucht wird,
weiterhin umfasst:
elektrisch Verbinden des Stromfilters;
Bereitstellen einer Zeitverzögerung;
Berechnen der angepassten durchschnittlichen Blindleistung, die sowohl von der Hilfsstromversorgung
wie auch von dem Stromfilter über den Zeitraum verbraucht wird; und
Abtrennen des Gleichstrom-Zwischenkreiskondensators.
6. Verfahren nach einem der Ansprüche 2-4, wobei ein fundamentaler Zyklus .02 Sekunden
lang ist und der Zeitraum ein oder mehrere fundamentale Zyklen umfasst.
7. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Stromfilter einer von
einem netzseitigen Stromfilter, einem maschinenseitigen dv/dt-Filter, oder ein Statorfilter
ist und der Defekt zumindest einer von einem Defekt in einer Sicherung, einem Defekt
in einem Kondensator, oder einem Defekt in einer Verbindung des Stromfilters ist.
8. System zum Bestimmen eines Defektes in einem Stromfilter (102) eines Windturbinengenerators
(30, 150), das System umfassend:
einen Computerprozessor (518); und
eine Mehrzahl von Sensoren (155, 160), die elektrisch mit dem Windturbinengenerator
und dem Computerprozessor verbunden sind; wobei
der Computerprozessor ausgeführt ist um:
eine Blindleistung die von dem Stromfilter verbraucht wird, basierend auf Daten von
den Sensoren, zu berechnen; und
die berechnete Blindleistung mit einem vorgegebenen Schwellenwert der Blindleistung
zu vergleichen, um den Defekt festzustellen,
wobei die Sensoren einen gemessenen Wert eines Wandlerschenkelstromes und einen einer
Wandlerschenkelspannung für jeden Phasendraht des Windturbinengenerators bereitstellen,
dadurch gekennzeichnet, dass
die gemessenen Werte bei einem Übergang von einem Vorladezustand zu einem Laufzustand
des Windturbinengenerators erhalten werden,
wobei der Vorladezustand im Vorladen eines Gleichstrom-Zwischenkreiskondensators,
der mit einem der Wandlerschenkel des Windturbinengenerators verbunden ist, besteht,
während der Stromfilter abgetrennt ist.
9. System nach Anspruch 8, wobei der Prozessor eine durchschnittliche Blindleistung,
die von einem Netzwandlerschenkel eines Windturbinengenerators über einen Zeitraum
verbraucht wird, berechnet.
10. System nach Anspruch 9, wobei der Prozessor weiterhin eine durchschnittliche Blindleistung,
die von einem Netzwandlerschenkel verbraucht wird, berechnet durch Anpassen der durchschnittlichen
Blindleistung, die von dem Netzwandlerschenkel verbraucht wird, mit einem Spannungsfaktor,
um eine angepasste durchschnittliche Blindleistung, die von dem Netzwandlerschenkel
verbraucht wird, zu bestimmen.
11. System nach einem der Ansprüche 8-10, wobei der Prozessor die von dem Stromfilter
verbrauchte Blindleistung berechnet durch:
Berechnen einer angepassten durchschnittlichen Blindleistung, die in dem Vorladezustand
von einer Hilfsstromversorgung des Windturbinengenerators verbraucht wird;
Berechnen einer angepassten durchschnittlichen Blindleistung, die im Laufzustand sowohl
von der Hilfsstromversorgung wie auch von dem Stromfilter verbraucht wird; und
Berechnen der durchschnittlichen Blindleistung, die alleine von dem Netzfilter verbraucht
wird, basierend auf den Werten der durchschnittlichen Blindleistung, die von der Hilfsstromversorgung
verbraucht wird, und der durchschnittlichen Blindleistung, die sowohl von der Hilfsstromversorgung
wie auch von dem Stromfilter verbraucht wird.
12. System nach Anspruch 11, wobei:
der Prozessor die angepasste durchschnittliche Blindleistung, die in dem Vorladezustand
von der Hilfsstromversorgung verbraucht wird, berechnet durch:
Verbinden des Gleichstrom-Zwischenkreiskondensators mit einem Wandlerschenkel des
Windturbinengenerators;
Vorladen des Gleichstrom-Zwischenkreiskondensators während der Stromfilter abgetrennt
ist; und
Erlangen der gemessenen Werte während des Vorladezustandes; und
der Prozessor die angepasste durchschnittliche Blindleistung, die im Laufzustand sowohl
von der Hilfsstromversorgung wie auch von dem Stromfilter verbraucht wird, berechnet
durch:
elektrisch Verbinden des Stromfilters;
Bereitstellen einer Zeitverzögerung;
Berechnen der angepassten durchschnittlichen Blindleistung, die sowohl von der Hilfsstromversorgung
wie auch von dem Stromfilter über den Zeitraum verbraucht wird; und
Abtrennen des Gleichstrom-Zwischenkreiskondensators.
13. Computer lesbares Medium beinhaltend Computerprogrammcode zum Bestimmen eines Defektes
in einem Stromfilter eines Windturbinengenerators, wobei der Computercode zum Betreiben
eines Verfahrens nach einem der Ansprüche 1 bis 7 ausgeführt ist.
1. Procédé destiné à déterminer un défaut dans un filtre de puissance (102) d'une génératrice
éolienne (30, 150), le procédé comprenant les étapes consistant à :
calculer une puissance réactive consommée par le filtre de puissance ; et
comparer la puissance réactive calculée à une puissance réactive seuil prédéfinie
pour déterminer ledit défaut, dans lequel ladite puissance réactive calculée est basée
sur une valeur mesurée d'un courant de branche de convertisseur et de l'une d'une
tension de branche de convertisseur pour chaque fil de phase de la génératrice éolienne,
caractérisé en ce que
lesdites valeurs mesurées sont obtenues lors d'un passage d'un état de pré-charge
à un état de marche de la génératrice éolienne, dans lequel l'état de pré-charge consiste
à pré-charger un condensateur de liaison CC connecté à l'une d'une branche de convertisseur
de la génératrice éolienne, alors que le filtre de puissance est déconnecté.
2. Procédé selon la revendication 1, dans lequel l'étape de calcul de la puissance réactive
consommée par le filtre de puissance comprend le calcul d'une puissance réactive moyenne
consommée par une branche de convertisseur de grille de la génératrice éolienne sur
une période de temps.
3. Procédé selon la revendication 2, dans lequel l'étape de calcul de la puissance réactive
moyenne consommée par une branche de convertisseur de grille comprend en outre l'ajustement
de la puissance réactive moyenne consommée par la branche de convertisseur de grille
par un facteur de tension afin de déterminer une puissance réactive moyenne ajustée
consommée par la branche de convertisseur de grille.
4. Procédé selon la revendication 1, dans lequel l'étape de calcul de la puissance réactive
consommée par le filtre de puissance comprend en outre:
le calcul d'une puissance réactive moyenne ajustée consommée dans ledit état de pré-charge
par une alimentation électrique auxiliaire (142) de la génératrice éolienne ;
le calcul d'une puissance réactive moyenne ajustée consommée par l'alimentation électrique
auxiliaire et le filtre de puissance dans ledit état de marche ; et
le calcul d'une puissance réactive moyenne consommée par le filtre de puissance seul
sur la base des valeurs de la puissance réactive moyenne consommée par l'alimentation
électrique auxiliaire et de la puissance réactive moyenne consommée par l'alimentation
électrique auxiliaire et le filtre de puissance.
5. Procédé selon la revendication 4, dans lequel:
l'étape de calcul d'une puissance réactive moyenne ajustée consommée par ladite alimentation
électrique auxiliaire dans ledit état de pré-charge comprend en outre:
la connexion du condensateur de liaison CC (125) à une branche de convertisseur de
ladite génératrice éolienne ;
la pré-charge dudit condensateur de liaison CC alors que ledit filtre de puissance
est déconnecté ; et
l'obtention desdites valeurs mesurées durant ledit état de pré-charge ;
l'étape de calcul d'une puissance réactive moyenne ajustée consommée par l'alimentation
électrique auxiliaire et le filtre de puissance dans ledit état de marche comprend
en outre:
la connexion électrique dudit filtre de puissance;
la fourniture d'un décalage temporel;
le calcul de ladite puissance réactive moyenne ajustée consommée par l'alimentation
électrique auxiliaire et le filtre de puissance sur ladite période ; et
la déconnexion dudit condensateur de liaison CC.
6. Procédé selon l'une quelconque des revendications 2-4, dans lequel un cycle fondamental
est de 0,02 seconde et la période de temps est de un ou plusieurs cycles fondamentaux.
7. Procédé selon l'une quelconque des revendications précédentes, dans lequel ledit filtre
de puissance est l'un d'un filtre de puissance côté grille, d'un filtre dv/dt côté
machine ou d'un filtre de stator, et ledit défaut est au moins l'une d'une défaillance
dans un fusible, d'une défaillance dans un condensateur ou d'une défaillance dans
une connexion dudit filtre de puissance.
8. Système pour détecter un défaut dans un filtre de puissance (102) d'une génératrice
éolienne (30, 150), le système comprenant:
un processeur informatique (518) ; et
une pluralité de capteurs (155, 160) électriquement connectés à ladite génératrice
éolienne et audit processeur informatique ; dans lequel
ledit processeur informatique est configuré pour:
calculer une puissance réactive consommée par le filtre de puissance sur la base de
données provenant desdits capteurs ; et
comparer la puissance réactive calculée à une puissance réactive seuil prédéfinie
pour déterminer ledit défaut, dans lequel lesdits capteurs fournissent une valeur
mesurée d'un courant de branche de convertisseur et de l'une d'une tension de branche
de convertisseur pour chaque fil de phase de la génératrice éolienne,
caractérisé en ce que
lesdites valeurs mesurées sont obtenues lors d'un passage d'un état de pré-charge
à un état de marche de la génératrice éolienne, dans lequel l'état de pré-charge consiste
à pré-charger un condensateur de liaison CC connecté à l'une d'une branche de convertisseur
de la génératrice éolienne, alors que le filtre de puissance est déconnecté.
9. Système selon la revendication 8, dans lequel ledit processeur calcule une puissance
réactive moyenne consommée par une branche de convertisseur de grille de la génératrice
éolienne sur une période de temps.
10. Système selon la revendication 9, dans lequel ledit processeur calcule en outre une
puissance réactive moyenne consommée par une branche de convertisseur de grille en
ajustant la puissance réactive moyenne consommée par la branche de convertisseur de
grille par un facteur de tension afin de déterminer une puissance réactive moyenne
ajustée consommée par la branche de convertisseur de grille.
11. Système selon l'une quelconque des revendications 8-10, dans lequel le processeur
calcule la puissance réactive consommée par le filtre de puissance en :
calculant une puissance réactive moyenne ajustée consommée dans un état de pré-charge
par une alimentation électrique auxiliaire de la génératrice éolienne ;
calculant une puissance réactive moyenne ajustée consommée par l'alimentation électrique
auxiliaire et le filtre de puissance dans un état de marche ; et
calculant la puissance réactive moyenne consommée par le filtre à grille seul sur
la base des valeurs de la puissance réactive moyenne consommée par l'alimentation
électrique auxiliaire et de la puissance réactive moyenne consommée par l'alimentation
électrique auxiliaire et le filtre de puissance.
12. Système selon la revendication 11, dans lequel:
ledit processeur calcule ladite puissance réactive moyenne ajustée consommée par ladite
alimentation électrique auxiliaire dans ledit état de pré-charge en : connectant le
condensateur de liaison CC à une branche de convertisseur de ladite génératrice éolienne
;
pré-chargeant ledit condensateur de liaison CC alors que ledit filtre de puissance
est déconnecté ; et
obtenant lesdites valeurs mesurées durant ledit état de pré-charge ; et
ledit processeur calcule ladite puissance réactive moyenne ajustée consommée par l'alimentation
électrique auxiliaire et le filtre de puissance dans ledit état de marche en :
connectant électriquement ledit filtre de puissance ;
fournissant un décalage temporel ;
calculant ladite puissance réactive moyenne ajustée consommée par l'alimentation électrique
auxiliaire et le filtre de puissance sur ladite période ; et
déconnectant ledit condensateur de liaison CC.
13. Support lisible par ordinateur contenant un code de programme informatique pour déterminer
un défaut dans un filtre de puissance d'une génératrice éolienne, le code informatique
étant configuré pour mettre en oeuvre le procédé selon l'une quelconque des revendications
1 à 7.